1. Technical Field
The present invention relates to a combustion engine that includes an exhaust pipe and a particle filter located therein. More particularly, the invention relates to a combustion engine having an exhaust pipe, a particle filter located in the exhaust pipe, and means for cleaning the filter. Furthermore, the invention relates to a method for cleaning a particle filter located in an exhaust pipe associated with a combustion engine.
2. Background of the Invention
Today's vehicle industry strives to utilize combustion engines that comply with higher and higher demands for purity of the emissions produced by the combustion processes that take place inside the engines. Particularly where combustion processes in diesel engines are concerned, soot and ash particles are one type of such emissions. In order to reduce the occurrence of soot and ash particles in the exhaust gases that are ultimately emitted into the ambient environment, particle filters can be installed in the exhaust pipe. The particle filters typically take the form of mechanical filters and, in principle, function as a screen that allows passage of certain exhaust gas components, for example, carbon dioxide and water, but which prevents the passage of soot and ash particles. This means that the soot and the ash particles will gradually form a deposit on the filter, which makes passage of the exhaust gases more difficult and results in an increase in back pressure at the filter. This also results in an increase of the fuel consumption of the vehicle. Should the process be allowed to proceed, the particle quantity finally becomes so large that the engine ceases to function. A traditional method for ensuring that the back pressure remains at an acceptable level is to replace the filter at regular intervals. In a combustion engine having a cylinder volume of seven liters, approximately one liter of particulate is produced over the course of approximately 70,000 kilometers (approximately 43,500 miles) of driving when operating on normal fuels. This means that filter replacement has to take place at relatively frequent intervals, something which might be perceived as awkward since it its desirable that vehicle service intervals not be too frequent.
Therefore, in order to increase the service life of the filter, it is desirable that the filter be cleaned in some way without having to dismantle the filter from the exhaust pipe. In this regard, trials have been performed with catalytic filters that are intended to perform catalytic combustion of the soot particles. This type of process, however, does not remove the ash deposit from the filter surface. Furthermore, as a result of the heat generated in the catalytic combustion process, there is a risk that the ash forms a cement-like material on the filter surface.